Doctoral Dissertations

Date of Award

12-2007

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Natural Resources

Major Professor

Siqun Wang

Committee Members

Adam M. Taylor, Brian K. Via, Ian D. Hartley, Timothy G. Rials, Xiaofei P. Ye

Abstract

The goal of this research was to investigate the influence of selected wood characteristics and composites production parameters on the sorption behavior of wood materials. A better understanding of the sorption behavior of different wood structures and types could be useful in protecting wood against wood deterioration. The differences among tree ring locations within the stem cross-section have not been explained in terms of sorption behavior. The purpose of the first task was to investigate the effect of differences among earlywood, latewood, and tree ring location within the stem crosssection on the water vapor sorption. A loblolly pine (Pinus taeda) tree was cut into earlywood and latewood from the 2nd to 50th tree rings. A sorption kinetics test was conducted from 11% to 89% RH. Results showed that earlywood had higher sorption rates and diffusion coefficients than latewood, while outer tree rings had higher sorption rates and diffusion coefficients than inner tree rings.

An understanding of sorption behavior of individual fibers with varying refiner pressure is necessary to better engineer wood fiber-based composites. The second task was to investigate water vapor sorption of refined fiber as affected by steam pressure using small-scale measurements. Juvenile and mature loblolly pine wood was refined at 2 to 18 bar of steam pressure. Fiber properties were determined by Scanning Electron Microscope (SEM), Dynamic Contact Angle (DCA), X-ray Diffraction (XRD), and a water activity meter. A sorption kinetics test was conducted from 11% to 89% RH. Higher rates of sorption were found in juvenile fiber refined under low steam pressure. Higher water activity and lower cystallinity was found at low-steam-pressure-refined fibers.

The volume of oriented strandboard (OSB) produced has significantly increased over the last few decades. Wood, resin, and wax play a key role in manufacture and inservice properties. How resin and wax affect the water vapor sorption behavior of resinated and waxed strands remain unclear. The third task was to investigate the effect of processing parameters on the sorption behavior of wood strands under varying environmental conditions. Loblolly pine strands were created with 2 to 4% and 0.5 to 1.5% for resin and wax loading. The resinated strand was pressed with different platen temperatures (120, 160, and 200°C) and compression rates (1.05 and 1.65). A sorption kinetics test was conducted from 11% to 89% RH. Higher resin and wax loading levels resulted in reduced water vapor sorption in early sorption periods. Higher press platen temperatures and compression rates also decreased the sorption properties of resinated loblolly pine strands. Wax loading had more influence on sorption properties than resin loading. Press platen temperatures had more influence on sorption behavior than compression rate.

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